Commonly assigned and co-pending U.S. published patent application no. 2006/0269027, the disclosure which is hereby incorporated by reference in its entirety, discloses a receiver that includes a matched filter and an M-of-N detector coupled to the matched filter output. The detector is employed to determine potential synchronization pulses occurring at least M times in N consecutive opportunities. The essential element of the co-pending application relevant to this application is that of the on-line noise estimation process for the constant false alarm rate (CFAR) detector. The previously disclosed noise estimator in U.S. Patent Publication No. 2006/0269027 used an outlier rejection scheme to delete samples from a data record that likely contained significant non-noise components. This approach can work well when the receiver can rely on a relatively large difference between samples that are noise-only and those that contain 1 or more signal components (e.g., high signal-to-noise (SNR) scenarios). However, the proposed method does have some shortcomings. For example, if the significant portions of data record collected are “contaminated” with signal, then the previous technique is unable to recover the noise processes for the purpose of noise power estimation to support the CFAR detection scheme.
New improvements are necessary. For example, in this disclosure, a posture of adopting “blind” signal processing is used (where blind means that the signals and noise are “unlabeled” to the receiver). Additionally, only a scalar (i.e., non-array) system is assumed. This means that traditional array processing techniques (e.g., beam-forming and nulling) are not applicable to aid in noise estimation. Lastly, the processing for noise power estimation is performed on-line or as an in-service estimator. The value of this property is well appreciated by those skilled in the art, but in short it means that the link need not reserve any specialized resources solely for aiding the signal receiving to estimate the noise processes needed for setting optimum receiver or link performance.
Assuming that the link noise can be blindly estimated in an in-service or on-line manner, then this estimate could be used to improve communication system efficiency or throughput by not only enabling adaptive modulation, but also for improving some blind source signal separation methods allowing by say allowing N sources to be separated by N sensors employing only second-order statistics, and blind adaptive thresholding for robust signal detection with various quality indicators in the presence of multiple interfering signals.